Method of producing 2-(chloromethyl) allyl-substituted silanes

ABSTRACT

When reacting chlorine with methallylsilanes, the yield of 2(chloromethyl)allylsilanes is increased substantially by carrying out the reaction in the absence of light or other sources of free radicals.

United States Patent Michael et al.

[54] METHOD OF PRODUCING 2- (CHLOROMETHYL) ALLYL- SUBSTITUTED SILANESInventors: Keith W. Michael; William E.

Dennis, both of Midland, Mich.

Assignee: Dow Corning Corporation, Midland,

Mich.

Filed: May 28, 1971 Appl. No.: 148,200

US. Cl. ..260/448.2 E, 260/4482 Q Int. Cl. ..C07f 7/08 Field of Search..260/448.2 B, 448.2 Q

References Cited UNITED STATES PATENTS 11/ 1968 Pope et a1. ..260/448.2E

Oct. 3, 1972 3,449,393 6/1969 Sattlegger et al....260/448.2 E

OTHER PUBLICATIONS Noll, Chemistry and Technology of Silicones, 2nd ed.,Academic Press, NY. (1968), pp. 150- 153.

[57] ABSTRACT When reacting chlorine with methallylsilanes, the yield of2-(chloromethyl)a1lylsilanes is increased substantially by carrying outthe reaction in the absence of light or other sources of free radicals.

5 Claims, No Drawings METHOD OF PRODUCING 2-(CHLOROMETHYL)ALLYL-SUBSTITUTED SILANES This invention relates to the reaction ofchlorine with methallylsilanes. More particularly, the present inventionrelates to an improved method for producing certain2-(chloromethyl)allyl-substituted silanes.

Chlorine reacts with methallyl-substituted silanes by two routes, bothby addition to form 2,3-dichloro-2- methylpropyl-substituted silanes andby substitution to form 2-(chloromethyl)allylsilanes. Because of thehigh reactivity of the allylic chloride, the 2-(chloromethyl)allylsilanes are valuable organofunctional silanes.Mironov et al., Khim Nauk, 461(1960) C.B. Translation 428, disclose thereaction of (2- methyl)allyltrichlorosilane with chlorine to obtainabout 25 percent yield of the addition product and 24 percent yield ofthe substitution product. The present method, wherein free radicals areexcluded from the reaction, gives much higher yields of the desiredsubstitution product.

Thus, in accordance with the invention, there is pro vided an improvedprocess for preparing 2- (chloromethyl)-allyl-substituted silanescomprising reacting chlorine with silanes of the formula in which X is achlorine or fluorine atom, R is an alkyl radical containing from one tosix inclusive carbon atoms, and n has a value of 2 or 3; the reactionbeing carried out at a temperature of no more than 165C. and in theabsence of free radicals. In addition, the reaction is carried out underconditions which allow liberated hydrogen chloride to be removed fromthe reaction mixture. v

As described above, the reactant silanes include cnsiomc=m olzsiomczom',ClzSlCHzC=CH CH3 CH3 CH3 CzHs CH and the like. These silane reactantsare readily prepared by the reaction of X R -nsil-l with 2,4,4trimethylpentene-l by methods well known in the art. If desired,mixtures of silanes can be used as the reactants in the present method.

The reaction of chlorine with the specified methallylsilanes can bedepicted as:

XfiiCHzC-CHgCl j Ra-n 2 (substitution product) Hydrogen chloride is alsoobtained as a byproduct of the substitution reaction. To avoid furtherreaction of the hydrogen chloride with the 2-(chloromethyl)allylsilaneproduct and resultant decreased yields, the liberated hydrogen chloridemust be removed from the reaction mixture. The removal of the acid ismost easily accomplished by conducting the reaction in an open systemwhereby the reactants are under atmospheric pressure. The open systemallows the liberation of HCl and facilitates its removal from thereaction mixture, as contrasted with a closed system, such as sealedmetal pressure vessel.

The other critical factor in obtaining increased yields of the2-(chloromethyl)allylsilane is minimization of the competing additionreaction. This is accomplished by carrying out the reaction attemperatures below 165C. and in the absence of free radical sources. Attemperatures above 165C., the generation of free radicals becomessignificant to the extent that yields are appreciably decreased. Optimumyields are obtained at temperatures of from 0 to 150C. External sourcesof free radicals which must be avoided include ultraviolet light, suchasdirect sunlight, peroxides in the reaction mixture, and radiation, suchas from a cobalt source. If desired, the reaction can be conducted inthe presence of oxygen or air which act as inhibitors for free radicalactivity. The reaction can be carried out in the presence of diffuselight in amounts insufficient to provide free radicals.

The reaction can be easily conducted by allowing chlorine to contact theliquid methallylsilanes such as by bubbling chlorine gas into a vesselof the silane or passing the reactants through a tube-type reactor. Itmay be necessary to remove the exothermic heat of reaction to maintainthe necessary low temperature. This can be accomplished by externalcooling means or by addition of an inert diluent, such as nitrogen. Thereaction can be carried out in nonreactive solvents, such as hexane orcarbon tetrachloride.

The product,

can be separated from the other reaction products by distillation orother means. The 2-(chloromethyl)allylsilane product can be used as acoupling agent to improve the interfacial bond strength of glass fibersand polypropylene, thus providing high strength glass reinforcedpolypropylene composite articles.

The following examples are illustrative and are not to be construed aslimiting the invention which is defined in the claims.

EXAMPLE 1 Methallyltrichlorosilane grams) was added dropwise to a14-inch glass condenser packed with glass wool and wrapped with blacktape to exclude light. The condenser was cooled with tap water 1 5 C.).The condenser, mounted vertically, was fitted with a gas inlet at thetop into which was fed a mixture of chlorine cc/min.) and nitrogen 120cc/min.). The reaction products wee collected in a vented flask at thebottom of the condenser.

Analysis of the products by vapor phase chromatography showed that 76percent of the reactant silane had been converted with ClgSiCHaC-O'HiClbeing present in a quantity 15 times greater than that of 01 EXAMPLE 2Methallyltrichlorosilane (25 grams) was added dropwise from a syringe tothe top of a 30-inch long, 41-inch diameter stainless steel tube. Thetube was fitted with a water jacket for cooling and a gas inlet at thetop. Chlorine was admitted at a rate of 90 cc/min. during the additionof the silane. The tube was not packed and nitrogen was not used as adiluent. Addition was completed after 20 minutes. The products werecollected in a vented flask. Analysis of the product showed 57 percentconversion of the reactant silane to monoand dichlorinated products;

01 ClgSlCHgC-CHzCl and C1aSiCH1( ]OHO1 Hz CH: being present in a ratioof 1, respectively.

EXAMPLE 3 Temp. Reaction Range Time ClaSiCNzii-CNzCI (C.) (1118.) fig 7These yields are to be compared to the prior art methods utilizingultraviolet light which give about -30 percent yield of the2-(chloromethyl)allylsilane. The silane reactant has a freezing point ofabout 20 C. but the reaction can be run at even lower temperatures bychoice of the proper solvent.

EXAMPLE 4 When F1 SiCHzC=CH2 CH3 CH3 for the silane reactant of Example1 and procedure of Example 1 is used, substantial yields of msromc-cm01e m o 11:

are obtained.

EXAMPLE 5 Trimethylformate (212 grams) was slowly added to 108 grams of2-(chloromethy1)allyltrichlorosilane. After addition, the mixture wasrefluxed for 44 hours. The product was distilled to obtain2-(chloromethyl)a1- lyltri-methoxysilane having a boiling point of 78C.]10 mm. Hg, n 5 of 1.4371 and d"? of 1.0646.

Glass cloth was immersed in an aqueous solution containing about 0.5weight percent of 2- (chloromethyl)-ally1trimethoxysilane. The glasscloth was air dried. Polypropylene laminates were formed using thissilane-treated glass and, for purposes of comparison, untreated glasscloth. The laminates were formed in a chase mold with two plies of glassseparating each sheet of polypropylene film. The film was 20 mils thick.The completed laminates consisted of eight sheets of polypropylene and14 plies of glass cloth, the glass cloth being laid in a unidirectionalvested manner. The lay-ups were placed in a hydraulic press and heatedto about 300F. The laminates were pressed for 20 minutes at 250 psi and485F.; then cooled in the press. Three samples of each type of laminatewere tested in flexure according to ASTM D790-63. The untreated glassresulted in a laminate flex strength of 14,000 psi as compared to 18,600psi obtained for the silane-treated glass reinforced laminate. Theapproximate 30 percent increase in strength demonstrates the utility ofthe silane as a coupling agent.

That which is claimed is:

1. A process for preparing 2-(ch1oromethy1)al1y1- substituted silanescomprising reacting chlorine with silanes of the formula in which X is achlorine or fluorine atom, R is an alkyl radical containing from one tosix inclusive carbon atoms, and n has a value of 2 or 3 while removinghydrogen chloride byproduct from the reaction mixture, said reactionbeing carried out at a temperature of no more than about 165C. and inthe absence of any source of free radicals.

2. The process of claim 1 wherein the reactant silane 3. The process ofclaim 1 wherein the reaction is carried out at a temperature in therange from about 0C. to about C.

4. The process of claim 1 wherein the reaction is carried out in thepresence of an inert diluent 5. The process of claim 4 wherein thediluent is nitrogen.

2. The process of claim 1 wherein the reactant silane is
 3. The processof claim 1 wherein the reaction is carried out at a temperature in therange from about 0*C. to about 150*C.
 4. The process of claim 1 whereinthe reaction is carried out in the presence of an inert diluent
 5. Theprocess of claim 4 wherein the diluent is nitrogen.